This disclosure is related to a shut-off valve and a hydraulic system. The shut-off valve and the hydraulic system will be described for use in an aircraft; however, the shut-off valve is amenable to other applications. Small business jets use an electrical motor driven pump to operate flight control devices such as aileron, elevator, and rudders. Small jets typically include a power system to operate devices that control landing gear retraction and extension, wheel brakes, nose wheel steering, and a speed brake which is a secondary system of the aircraft.
Because of using the electrical motor driven pump, minimizing internal leakage of hydraulic fluid in the system can be very important. A large amount of leakage can require the electrical motor driven pump to turn off and on frequently. Turning the electrical pump on and off frequently reduces the life of several components including the electrical motor, the hydraulic pump, hydraulic system parts, as well as electrical power generator system components since driving the electrical motor can generate a high in rush current voltage and hydraulic pressure spikes.
In the event of a pump and/or electrical system failure, accumulators hold hydraulic fluid volume enough to stop the aircraft on the ground. Accumulator sizing is driven by internal leakage of the hydraulic system.
Also, most business jets use anti-skid control systems. Most anti-skid control systems use hydraulically operated servo-valves. Since most servo-valves use jet pipe and nozzle-flapper mechanisms, the internal hydraulic leakage is relatively high. Typically, electrically driven shut-off valves can be used to prevent internal leakage for the servo-valve. Brake metering valves can also create internal leakage.
One means to reduce internal leakage is using a shut-off valve upstream of the brake metering valve. The shut-off valve can reduce the internal leakage. Electronic solenoids can be used to drive the shut-off valve. Electronic solenoid valves that open and close hydraulic fluid flow into the brake metering valves step in a manner that creates hydraulic pressure spikes to the brake system and large acoustic noise can be created each time the shut-off valve opens and closes.